1. Field of the Invention
This invention relates to calorimetry, and more specifically to calorimetric measurements made by combining flow rate and temperature signals.
2. Background Information
Heat meters, often referred to as BTU meters or net energy flow meters, determine the heat energy flow of a heat exchanger by measuring the flow rate of the heat exchanger fluid and the difference in temperature across the heat exchanger and by multiplying those measured quantities by factors selected to represent the specific heat of the fluid. The specific heat factor is generally selected based on a measured or presumed composition of the fluid and corrected for temperature.
In a practical application, such as an apartment building where a heat metered hydronic heating system has been installed, the water-based working fluid composition may not remain constant. This may be because of loss of some of the working fluid and replacement of it by a different fluid; because of chemical changes of one or more of the working fluid's components; or because of accumulation of debris in the plumbing system. As a result of any of these or other causes, the specific heat of the fluid can change from the value originally assumed, so that the heat meter no longer measures heat transfer accurately.
In U.S. Pat. No. 6,241,383 the inventor describes heat maintenance monitoring instrumentation for measuring the heat transfer between a heated surface and a heat transfer fluid to determine the condition of the heated surface to determine when maintenance is required. The disclosure of U.S. Pat. No. 6,241,383 is incorporated herein by reference.
In U.S. Pat. No. 6,023,969 and U.S. Pat. No. 5,948,978 the inventor describes instrumentation for providing, controlling and measuring the power to, and sensing the temperature of heated temperature sensors for the purpose of making a flow rate measurement using flow modulation. The disclosures of U.S. Pat. No. 6,023,969 and U.S. Pat. No. 5,948,978 are incorporated herein by reference.